Potentiometer



Nov. 28, 1961 J. MAIR 3,011,142

POTENTIOMETER Filed Dec. e, 1959 2 sheets-sheet 1 I3 2o |5 45 2O I6 n4l2 |4\ a 2 H` W F1' E' 5 5 5o 7 463i 9 25 57v 24 A 55 s y /////LI m 2722 4a ,2, u 52 5a IN V EN TOR.

JOSEPH MAI/i Nov. 28, 1961 J, MAIR 3,011,142

POTENTIOMETER Filed Dec. 8, 1959 2 Sheets-Sheet 2 IN V EN TOR.

JOSEPH MAI/'P United States Patent 3,011,142 Patented Nov. 28., 1961thee 3,011,142y POTENTIOMETER f Joseph Mair, 1090 Briarcliff Road,Monrovia, Calif.

n Filed Dec. 8, 1959, Ser. No. 858,202

7 Claims. (Cl. SSS-174) This invention relates to variable resistancedevices of the class of potentiometers and more particularly relates toa rotary type dual potentiometer or variable resistance apparatus foruse in computers, aircraft, guided missiles and similar mechanisms.

A precision type of potentiometer should not only have a high linearitycharacteristic and a low noise characteristic, but it should be simplein construction, rugged, compact, light in weight and should berelatively immune to shock. It should also be highly responsive to a lowtorque so as to insure accurate performance.

A An objective of the present invention is to provide a compact rotarytype of dual potentiometer that efficiently utilizes the space .that isnormally available in single unit potentiometers more advantageously,thereby .reducing the space requirement of such a potentiometer to about50% of that normally required by two single potentiometer units.

, Another objective of this invention is to provide a'dual potentiometerthat can materially reduce the weight requirernent by one third overtheweight normally required by two single'potentiometers in separateunits.

A further'objective of this invention is to provide a novel rotary typeof dual potentiometer wherein the wipers that cooperate with theirrespectivel resistance units are mounted on a shaft so that they areangularly 180 apart at all times. This balances the drag of the wipersand reduces the torque, both starting and running, that must be appliedto the shaft to vary the resistance of each unit as required.

tAn additional objective is to provide a dual potentiometer unit havingan extennal construction adapted to permit gauging any desired number ofdual potentiometer units so thatthese will all be operated by a singleshaft; this external construction including appropriate grooves adaptedto receive circular clamps adapted to secure the ganged units togetherin phased relationship. l

Another objective of the invention. is to provide a rotary rtype of dualpotentiometer wherein the external clamping arrangement is designed topermit the annular clamps to be flush with the external surface of thecasing when the clamps are in place, with the exception of the endclamps that hold the ends of the clamp together. This arrangementpermits easy external phasing of the dual individual potentiometer unitswhenever it is desired to gang a number of dual units together.

The rotary type of dual potentiometer unit according to this inventioncomprises an external casing which is closed at one end by acooperatingend platehaving an internal axial bearing or bushing housing.Theopposite end of the casing is closed by a second cooperating endplate that also is provided with an internal axial bearing or bushinghousing andphas a central borey adapted to permit passage of a. shaft. Apair of circular resistances are mounted within the casing so that eachone of the resistors is located near one end of the supporting casing,each of the resistors being in spaced relationship to the other and eachresistor being insulated rfrom the casing. The cir-` cular resistors areplaced within the casing so that they are axially positioned; eachcircular resistor substantially fills the entire circle and the smallgaps formed by the ends of the resistors are positioned angularly sothat the small gap of one resistor is located 180 from the gap of thesecond'resistor of each dual potentiometer unit.L

. There lis mounted on the shaft, for each dual unit op- 2 erated by theshaft, a rotor made of insulating material on which are carried, inspaced relationship to each other, two conductive slip ringsprovidedrwith a preferably V-shaped groove. These two slip rings areinsulated from each other. A stationary brush element rides in itsappropriate slip ring groove and is connected to a suitable brushterminal, secured to the wall of the casing and projecting therefrom.Each rotor is also provided with a suitable wiper support or arm foreach resistance element. The wipers or wiper supports kare in electricalcontact with the respective slip ring and the wipers or the wipersupports as the case may be are positioned in each dual unit so thatthey bear to each other an angular relationship of 180. The ends of eachcircular resistance unit are connected to appropriate terminalsrespectively, each of the corresponding end terminals are adja- V i centto its xed `brush terminal. This provides in a dual potentiometer unittwo groups of three terminals each; these protrude from the outersurface of the casing at opposite ends of a respective diameter.

The .foregoing and subsequent description can be better understood andvisualized by referring to the. accompanying drawings in which:

. FIG. 1 is an end plan view showing a dual potentiometer funit with anaxial shaft extending through thecasf,

ing and further showing the conventional position of the two sets ofthree terminals.

FIG. 2 is a cross section view of a single dual potentiometer unit withthe end caps in place taken on the line 2-2 of FIG. 1.

FIG. 3 is an end elevation of a rotor, shaft and resistor wipers whenviewed from the extending shaft end. The resistors are shown by thedotted lines and show how the ends are in opposition. n

FIG. 4 is a side elevation showing the relationshipof the shaft, rotor,slip rings, wiper arms and wipers that were yshown in FIG. 3. l t

FIG. 5k is a cross section view illustrating how a plurality of dualpotentiometer units may be ganged on a single shaft.

Referring to the drawings, FIGS. 1 and 2 show a single dualpotentiometer uniticomprising a casing 10 having a narrow internalcircumferential groove llrcounterbored from one end; the opposite end ofthe casinghas a corresponding external circumferential groove 12.`Groove 11 is adapted to receive cooperating groove 12 of a second casingor end plate. Adjoining theinner end of groove 12 there is a narrowgroove 13 that is larger in diameter than groove 12 and terminates in aslightly deeper narrowgroove 14 which does not extend to the surface ofgroove 12. Ylhe outer external surface of cas- FIG. 1 2.8.18 and 19, aresecured together by means of a suitable fastener` such as screw 20,after the clamp has been properly seated in the grooves. Since the innersurface of the longer ends of the clamp that fit in grooves 14 and 16are slightly tapered, they tend to clamp the f two .casings radially andlongitudinally together whenever the clamping annulus is pulledtightlyaround the grooves by screw 20. A

- End cap 21 has anaxial bearing or bushing recess 22 in which there isseated a ball bearingor bushing 23. vThe outer external surface of cap21, adjacent the end from which bushing recess 22 extends, is alsoprovided with a mating groove 12 and a shallower groove 13 thatcorresponds to groove 13 on the casing and also ends in a slightlydeeper groove 14. This permits clamping ring 17 to secure end cap 21 tothe cooperating end of a casing 10.

A second end cap 2.4 having a counterbored groove 11 at one end is alsoprovided with a narrow external groove 15, corresponding to groove 15 ofa casing, that extends inwardly and terminates in a slightly deepergroove 16. This permits cap 24 to close the other end of casing 10. Theend of cap 24 from which counterbore 11 extends, is provided with anaxial bearing or bushing recess 25 in which there is seated a ballbearing or bushing 26. A bore 27 extends axially through the center ofbearing recess 25 and continues through the end of the cap. Bore 27permits passage of a shaft 28 which is supported by bearings or bushings23 and 26, and is slightly larger than the diameter of the shaft so asnot to bind it.

Inside and adjoining the coupling portions 11 and 12, the inner surfaceof the casing is provided with a groove 29 and a groove 30 in which arefitted insulating rings 31 'and' 32. A first circular resistor,preferably in the form` of a mandrel Wound resistance element 33, is supported by insulator 31 and a second circular resistor 34v in the form ofa mandrel wound resistance element is supported by insulator 32. Theinner surfaces of the circular resistance elements 33- and 34 arecoaxial with shaft 28. One end 36 of circular resistance element 33 isconnected to insulated terminal 37 of FIG. l, and Ithe other end 38 ofcircular resistor 33 is connected to insulated terminal 39. Similarlyone end 40 of circular resistor 34 is connected to insulated terminal 41and the other end 42 of circular resistor 34 is connected to terminal43. The gaps between the ends of circular resistor elements 33 and 34are positioned within the casing on their respectiveinsulator so thatthe gaps bear an angular relationship of 180 to each other. While thepreferred resistor element is a mandrel wound circular coil it 4isintended that any other suitable type of circular resistor could beemployed in place of resistors 33 and 34.

A rotor element 44 made of suitable nonconducting insulating material issecured on shaft 28 by any suitable means such as keying, press fitting,splining, or a locking screw. Rotor element 44 is substantiallycylindrical and has a central projecting annulus 45 that is narrow inVwidth and serves to insulate and separate slip rings 46 and 47 from eachother when these are in position on the outer surface of rotor 44. Sliprings 46 and 47 are made of an electrical conducting material having alow resistance and each slip ring is provided with a preferably V-shapedgroove designated by the numerals 48 and 49 respectively.

A resilient brush is secured to a terminal 51 which extends from casing10 and is adjacent terminals 37 and 39 as shown in FIG. l. Resilientbrush 50 rides in V-shaped groove 48. A second resilient ybrush 52 issecured to terminal 53 that extends from casing 10 and is adjacentterminals 41 and 43; Ibrush 52 rides in V- shaped groove 49.

A wiper arm support S extends radially outwardly fromr one end of rotor44 and makes contact with slip ring 46. A second wiper supporting arm 56extends radially outwardly from the other end of rotor 44 and makeselectrical contact with slip ring 47. Arrn 5S is positioneddiametrically opposite to arm 56 but at the opposite end of the rotor. Afirst wiper 57, preferably of low resistance precious metal, is securedto the end of Y arm 55 and a second and similar wiper 5S is secured tothe end of arm 56. That portion of each wiper that cornes in contactwith the inner surface of the circular resistance elements is preferablyshaped to resemble a V andv is` preferably located near or at the end ofthe wiper.

The bottom of each V is curved slightly and assists the wiper in slidingsmoothly along the circular resistor contact surface with a minimum ofdrag. The length of the wipers is uniform and this is adjusted so thatthe \/shaped contact portions press against the inner surface of thecircular resistor element with sufficient pressure; this is preferablyadjusted so that the wipers will exert approximately 4 mg./ inches offorce. Arms 55 and 56 may be -long or short depending on the diameter ofthe particular potentiometer casing that is employed. Since the arms are180 apart, the wipers that are secured to the arms will also have theV-shaped contact portions located 180 apart.

FIG. 5 shows a cross section view of a combination of three rotary typedual potentiometer units ganged on a single shaft. This arrangementprovides six individual potentiometers. As many dual units can be gangedon one shaft as can be satisfactorily supported by that shaft.Combinations have been assembled that contained thirty dualpotentiometer units; such an arrangement made available sixty individualresistances which could all be operated by a single shaft after they hadbeen properly phased in.

The phasing of each potentiometer unit is accomplished by simplyloosening screw 20 of the appropriate annular clamp 17 and rotating thecasing until that particular unit showed the proper resistances for thesetting of the shaft.

The operation of the dual potentiometer according to this invention isas follows: wipers 57 and 58 ride against the inner surface of thecircular resistance means as the shaft is rotated and since the circularresistance means is coaxial with the shaft the wiper will exert thecorrect pressure at all times. The current that will flow at anyposition is controlled by the amount of resistance that is between thewiper contact and the end of the circular resistor. The fixed resilientbrush being always in contact with its respective slip ring, willcomplete the circuit between the wiper contact and the terminal iat theend of the resistor.

The amount of rotation that the rotor and Wiper assembly make inreaching from one end of the resistor to the other varies depending onthe particular specifications for various sized potentiometers. Thisusually varies from 351 to 358 and is partly dependent on the size ofthe potentiometer as well as the diameter ofthe resist# ance wireforming the circular resistor.

The novel dual potentiometer unit makes it possible t0. utilize tworesistors in the space that is normally required for a single resistanceelement due to the improved construction. This reduces the spacerequirement about 50% and the weight requirement about 33%. Balancingthe drag of wipers on opposite sides of the rotor also reduces thestarting and continuing torque and permits smoother, delicate and moresensitive adjustment of the resistances required. l

It is to be understood that various alterations may be made in thedetails of construction without departing from the scope of the presentinvention as defined by the following claims.

I claim:

1. A rotary variable Vresistance device comprising: a

Y casing having a longitudinal axis; a first circular resistance meanscarried in said casing, concentric with said axis and insulated fromsaid casing; a second circular resistance means carried in said casing,concentric with said axis and insulated from said casing, said first andsecond circular resistance means being in spaced relationship with eachother, the ends of the rst circular resistance means being positioned insaid casing so that they bear an angular relationship of to thecorresponding ends of the second circular resistance means; a shaftaxially supported within said casing and capable of rotation therein; aninsulator rotor secured to said shaft; a first slip ring and a secondslip ring concentrically mountadapted to engage said first slip ring; asecond brush means adapted to engage said second slip ring; a firstwiper means connected to said tirst slip ring and adaptedv to makecontact with said first circular resistance means; a second wiper meansconnected to said second slip ring and adapted to make contact with saidsecond circular resistance means,v said first and second wiper meansbearing an angular relationship of 180 rto each other; means for makingexternal connection with each end of the first circular 4resistancemeans and with said first brush means; and means for making externalconnection with each end of' the second circular resistance means andwith said second brush means. X y

2. A rotary variable resistance devicecomprising: a casing having alongitudinal axis; a first circular resistance means carried in jsaidcasing, concentric with said axis and insulated from said casing; asecond circular resistance means carried in said casing, concentric withsaid axis and insulated from said casing, said first and second circularresistance means being in spaced relationship with each other, the endsof the first circular resistance means Ibeing positioned in said casingso that they bear an angular relationship of 180 to the correspondingends of the second circular resistance means; a shaft axially supportedwithin said casing and capable of rotation therein; an insulator rotorsecured to said Shaft; a first slip ring and a second slip ringconcentrically mounted on said insulator rotor, said first and secondslip rings being insulated from each other; a first brush means adaptedto engage said first slip ring; a second brush means adapted to engagesaid second slip ring; a first wiper means connected to said first slipring and adapted to make contact with said first circular resistancemeans; a second wiper means connected to said second slip ring andadapted to make contact with said second circular resistance means, saidfirsty and second wiper means bearing an angular relationship of 180 toeach other; a terminal means externally associated with said casingadapted to make connection with one end of the first circular resistancemeans; a terminal means externally associated with said casing adaptedto make connection with the other end of the first circular re` sistancemeans; a terminal externally associated with said casing adapted to makeconnection with said first brush means; a terminal means associa-tedexternally with said casing adapted to make connection with one end ofthe second circular resistance means; a terminal means externallyassociated with said casing adapted to make connection with the otherend of said second circular resistance means; and terminal meansassociated externally with said casing adapted to make connection withsaid second brush means.

3. A rotary variable resistance device comprising; a casing having alongitudinal axis; a first circular resistance means carried in saidcasing, concentric with said axis and insulated from said casing; asecond circular resistance means carried in said casing, concentric withsaid axis and insulated from said casing, said first and second circularresistance means being in spaced relationship to each other, the ends ofthekfirst circular resistance means being positioned in said casing sothat they n bear an angular relationship of 180 to the correspondingends of the second circular resistance means; a first closure memberadapted to engage one end ,oisaid casing; a second closure memberadapted to engage the other end of said casing, said second closuremember being provided with an axial bore; a shaft; means associated withsaid first and second closure members for axially and rotatablysupporting said shaft within said casing, said shaft extending throughsaid axial bore in said second closure member; an insulator rotorsecured i to said shaft between said first'and -second closure members;a `first and a second slip ring secured to said insulator rotor and inspaced relationship to each other and insulated from each other; a firstbrush means adapted to engage the first slip ring; a second brush meansadapted to engage the Second slip ring; a first wiper means connected`to the first slip ring and adapted to make contact with thefirstcircular resistance means; a second wiper means connected with thesecond slip ring and adapted to make Contact with the second circularresistance means, said first and second wiper means bearing anangularrelationship of' 180 to each other; means for making external connectionwith each end of the first circular resistance means and with the firstbrush means; and means formaking external connection with each end ofthe second circular resistance means and with the second brush means. i

4. A rotary variable resistance device according to claim 3 wherein eachend of the casing is provided with means for axially attaching anothercooperating casing thereto; and locking means associated with each endof said cooperating casings adapted rto hold each pair of cooperatingcasings in longitudinal and radial relationship with each other.

5. A rotary variable resistance device comprising; a

plurality of cooperating casings, each casing having a longitudinalaxis; a first circular resistance means, concentric with said respectiveaxis in each of said casings, each of said circular resistance meansbeing insulated from its respective casing; a second circular resistancemeans, con-k n casings in said assembled plurality of cooperatingcasings;

a second closure member adapted to engage the open end of the other ofthe end casings in said assembled plurality of cooperating casings, saidsecond closure member having an axial bore; a shaft; means associatedwith said first and second closure members for axially and rotatablysupporting said shaft within said plurality of cooperating casings, saidshaft extending through said axial bore inthe second closure member; aplurality of insulator'4 rotors secured to said shaft, one rotor beingadapted to cooperate with its corresponding casing; a first and a secondslip ring secured to each of said insulator rotors; said first andcorresponding second slip rings being insulated from each other; a firstbrush means associated Witheach of said casings and adapted to engageits corresponding first slip ring; a second brush means associated witheach of said casings and adapted to engage its corresponding second slipring; a first wiper means associated with each of said rotor insulatorsin contact with its respective first slip ring and adapted to contactits respective first circular resistance means; a second wiper meansassociated with each of said rotor insulators in contact with itsrespective second slip ring vand adapted to Contact with its respectivesecond circular resistance means, each pair of cooperating first andsecond wiper means bearingan angular relationship of to each other;means associated with each individual casing adapted to permit externalconnection with each end of eachrrespcctive first circular resistancekmeans and with each respective first brush means; and 'means associatedwith each individual casing adapted to permit external connection witheach end of each respective second circular resistance means and witheach respective second brush means.

6.y A rotary variable resistance device according to claim 5 whereinlocking means are associ-ated with each end of` cooperating casingsadapted to secure said casings in axial, `longitudinal and radialrelationship to each other.

7. A rotaryV variable resistance device comprising, a casing having alongitudinal axis; means at each end of said casing for coupling saidcasing to the cooperating ends of a corresponding casing and tocooperating closure members; a first circular resistance means carriedin said casing, concentric with said axis and insulated from saidcasing; a second circular resistance means carried in said casing,concentric with said axis and insulated from said casing, said first andsecond circular resistance means being in spaced relationship With eachother, the ends of the rst circular resistance means being positioned insaid casing so that they bear an angular relationship of 180 to thecorresponding ends ofthe second circular resistance means; a shaftaxially supported within said casing and capable of rotation therein; aninsulator rotor secured to said shaft; a first slip ring and a secondslip ring concentrically mounted on said insulator rotor, said first andsecond slip rings being insulated from each other; a rst.

brush means adapted to engage said rst slip ring; a second brush meansadapted to engage said second slip ring; a irst Wiper means connected tosaid first slip ring and adapted to make Contact with said firstcircular resistance means; a second Wiper means connected to said secondslip ring and adapted to make contact with said second crcularresistance means, :said rst and second Wiper means bearing an angularrelationship of 180 to each other; means for making external connectionwith each end of the iirst circular resistance means and With said rstbrush means; and means for making external connection with each end ofthe second circular resistance means and with said second brush means.

Sparrow Apr. 25, 1950-

